【HDU 3911】Black and White 线段树 最长连续1个数

博客介绍了如何利用线段树解决HDU 3911题目,该题涉及01序列和区间操作。通过定义连续1和0的线段树结构体,实现对序列的查询和反转操作,从而找到最长连续1的子序列。

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HDU 3911
题意 给你一个包含 n n n元素的01序列 有m次操作 0操作 输出 x 到 y 之间最长1个数
1 操作 将x y 区间内所有数取反
这道题去年六月份写过题解 不过是看不懂的一句话题解 今天重新总结一下这个题
类似这种区间可以通过一种性质 (左边,右边,中间)得到的题 我们用线段树去做
这题我们定义两个结构体 arr1 和 arr2 arr1就是原序列中 连续 1 的一颗树
arr2 就是 原序列中 连续 0的一棵树
你既然 1 操作使得一段区间反转 那么直接 1树和0树换一下即可
这是十个月前的有毒代码

#include <cstdio>
#include <cstring>
#include <iostream>
#include <queue>
#include <cmath>
#include <map>
#include <stack>
#include <set>
#include <sstream>
#include <vector>
#include <stdlib.h>
#include <algorithm>
using namespace std;

#define dbg(x) cout<<#x<<" = "<< (x)<< endl
#define dbg2(x1,x2) cout<<#x1<<" = "<<x1<<" "<<#x2<<" = "<<x2<<endl
#define dbg3(x1,x2,x3) cout<<#x1<<" = "<<x1<<" "<<#x2<<" = "<<x2<<" "<<#x3<<" = "<<x3<<endl
#define max3(a,b,c) max(a,max(b,c))
#define min3(a,b,c) min(a,min(b,c))
#define lc (rt<<1)
#define rc (rt<<11)
#define mid ((l+r)>>1)

typedef pair<int,int> pll;
typedef long long ll;
const int inf = 0x3f3f3f3f;
const int _inf = 0xc0c0c0c0;
const ll INF = 0x3f3f3f3f3f3f3f3f;
const ll _INF = 0xc0c0c0c0c0c0c0c0;
const ll mod =  (int)1e9+7;

ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll ksm(ll a,ll b,ll mod){int ans=1;while(b){if(b&1) ans=(ans*a)%mod;a=(a*a)%mod;b>>=1;}return ans;}
ll inv2(ll a,ll mod){return ksm(a,mod-2,mod);}
int Max(int a,int b)
{
    if(a>b) return a;
    return b;
}
int Min(int a,int b)
{
    if(a<b) return b;
    return a;
}
const int MAX_N = 100025;
struct node
{
    int len_l,len_r,len,down;
}arr1[MAX_N<<2],arr0[MAX_N<<2];
void up(int rt,int l,int r)
{
    arr1[rt].len_l = arr1[rt<<1].len_l;
    if(arr1[rt].len_l==mid-l+1) arr1[rt].len_l+=arr1[rt<<1|1].len_l;
    arr1[rt].len_r = arr1[rt<<1|1].len_r;
    if(arr1[rt].len_r==r-mid) arr1[rt].len_r+=arr1[rt<<1].len_r;
    arr1[rt].len = Max(arr1[rt<<1].len,arr1[rt<<1|1].len);
    arr1[rt].len = Max(arr1[rt].len,Max(arr1[rt<<1].len_r+arr1[rt<<1|1].len_l,Max(arr1[rt].len_l,arr1[rt].len_r)));

    arr0[rt].len_l = arr0[rt<<1].len_l;
    if(arr0[rt].len_l==mid-l+1) arr0[rt].len_l+=arr0[rt<<1|1].len_l;
    arr0[rt].len_r = arr0[rt<<1|1].len_r;
    if(arr0[rt].len_r==r-mid) arr0[rt].len_r+=arr0[rt<<1].len_r;
    arr0[rt].len = Max(arr0[rt<<1].len,arr0[rt<<1|1].len);
    arr0[rt].len = Max(arr0[rt].len,Max(arr0[rt<<1].len_r+arr0[rt<<1|1].len_l,Max(arr0[rt].len_l,arr0[rt].len_r)));
}
void SWAP(int rt)
{
    int len_l = arr1[rt].len_l;
    int len_r = arr1[rt].len_r;
    int len = arr1[rt].len;
    arr1[rt].len_l = arr0[rt].len_l;
    arr1[rt].len_r = arr0[rt].len_r;
    arr1[rt].len = arr0[rt].len;
    arr0[rt].len_l = len_l;
    arr0[rt].len_r = len_r;
    arr0[rt].len = len;
}
void down(int rt,int l,int r)
{
    if(arr1[rt].down)
    {
        arr1[rt].down^=1;
        arr1[rt<<1].down^=1;
        arr1[rt<<1|1].down^=1;
        SWAP(rt<<1);
        SWAP(rt<<1|1);
    }
}
void build(int rt,int l,int r)
{
    arr1[rt].len_l = arr1[rt].len_r = arr1[rt].down = arr1[rt].len = 0;
    arr0[rt].len_l = arr0[rt].len_r = arr0[rt].down = arr0[rt].len = 0;
    if(l==r)
    {
        scanf("%d",&arr1[rt].len);
        if(arr1[rt].len)
        {
            arr1[rt].len_l = arr1[rt].len_r = 1;
        }
        else
        {
            arr0[rt].len_l = arr0[rt].len_r = arr0[rt].len = 1;
        }
        return ;
    }
    build(rt<<1,l,mid);
    build(rt<<1|1,mid+1,r);
    up(rt,l,r);
}
void update(int rt,int l,int r,int x,int y)
{
    if(x<=l&&r<=y)
    {
        arr1[rt].down^=1;
        SWAP(rt);
        return ;
    }
    down(rt,l,r);
    if(x<=mid) update(rt<<1,l,mid,x,y);
    if(mid<y) update(rt<<1|1,mid+1,r,x,y);
    up(rt,l,r);
}
node query(int rt,int l,int r,int x,int y)
{
    if(x<=l&&r<=y)
        return arr1[rt];
    down(rt,l,r);
    if(x<=mid&&y>mid)
    {
        node tmp1 = query(rt<<1,l,mid,x,y);
        node tmp2 = query(rt<<1|1,mid+1,r,x,y);
        node ans;
        ans.len_l = tmp1.len_l,ans.len_r = tmp2.len_r;
        if(ans.len_l==mid-l+1) ans.len_l+=tmp2.len_l;
        if(ans.len_r==r-mid) ans.len_r += tmp1.len_r;
        ans.len = Max(tmp1.len,tmp2.len);
        ans.len = Max(ans.len,Max(tmp1.len_r+tmp2.len_l,Max(ans.len_l,ans.len_r)));
        return ans;
    }
    else if(x<=mid)
    {
        return query(rt<<1,l,mid,x,y);
    }
    else if(x>mid)
    {
        return query(rt<<1|1,mid+1,r,x,y);
    }
}
int main()
{
    //ios::sync_with_stdio(false);
    //freopen("a.txt","r",stdin);
    //freopen("b.txt","w",stdout);
    int n,Q,opt,x,y;
    while(scanf("%d",&n)==1)
    {
        build(1,1,n);
        scanf("%d",&Q);
        while(Q--)
        {
            scanf("%d%d%d",&opt,&x,&y);
            if(opt==1)
            {
                update(1,1,n,x,y);
            }
            else
            {
                printf("%d\n",query(1,1,n,x,y).len);
            }
        }
    }
    //fclose(stdin);
    //fclose(stdout);
    //cout << "time: " << (long long)clock() * 1000 / CLOCKS_PER_SEC << " ms" << endl;
    return 0;
}

The second

#include <cstdio>
#include <cstring>
#include <iostream>
#include <queue>
#include <cmath>
#include <map>
#include <stack>
#include <set>
#include <sstream>
#include <vector>
#include <stdlib.h>
#include <algorithm>
using namespace std;

#define dbg(x) cout<<#x<<" = "<< (x)<< endl
#define dbg2(x1,x2) cout<<#x1<<" = "<<x1<<" "<<#x2<<" = "<<x2<<endl
#define dbg3(x1,x2,x3) cout<<#x1<<" = "<<x1<<" "<<#x2<<" = "<<x2<<" "<<#x3<<" = "<<x3<<endl
#define max3(a,b,c) max(a,max(b,c))
#define min3(a,b,c) min(a,min(b,c))
#define lc (rt<<1)
#define rc (rt<<11)
#define mid ((l+r)>>1)

typedef pair<int,int> pll;
typedef long long ll;
const int inf = 0x3f3f3f3f;
const int _inf = 0xc0c0c0c0;
const ll INF = 0x3f3f3f3f3f3f3f3f;
const ll _INF = 0xc0c0c0c0c0c0c0c0;
const ll mod =  (int)1e9+7;

ll gcd(ll a,ll b){return b?gcd(b,a%b):a;}
ll ksm(ll a,ll b,ll mod){int ans=1;while(b){if(b&1) ans=(ans*a)%mod;a=(a*a)%mod;b>>=1;}return ans;}
ll inv2(ll a,ll mod){return ksm(a,mod-2,mod);}
int Max(int a,int b)
{
    if(a>b) return a;
    return b;
}
int Min(int a,int b)
{
    if(a<b) return a;
    return b;
}
void Swap(int &x,int &y)
{
    int t = x;
    x = y;
    y = t;
}
const int MAX_N = 100025;
struct node
{
    int down,ls0,rs0,ls1,rs1,ms0,ms1;
}arr[MAX_N<<2];
void up(int rt,int l,int r)
{
    arr[rt].ls1 = arr[rt<<1].ls1;
    arr[rt].rs1 = arr[rt<<1|1].rs1;
    if(arr[rt].ls1==mid-l+1) arr[rt].ls1+=arr[rt<<1|1].ls1;
    if(arr[rt].rs1==r-mid) arr[rt].rs1+=arr[rt<<1].rs1;
    arr[rt].ms1 = Max(arr[rt<<1].ms1,arr[rt<<1|1].ms1);
    arr[rt].ms1 = Max(arr[rt].ms1,Max(Max(arr[rt].ls1,arr[rt].rs1),arr[rt<<1].rs1+arr[rt<<1|1].ls1));

    arr[rt].ls0 = arr[rt<<1].ls0;
    arr[rt].rs0 = arr[rt<<1|1].rs0;
    if(arr[rt].ls0==mid-l+1) arr[rt].ls0+=arr[rt<<1|1].ls0;
    if(arr[rt].rs0==r-mid) arr[rt].rs0+=arr[rt<<1].rs0;
    arr[rt].ms0 = Max(arr[rt<<1].ms0,arr[rt<<1|1].ms0);
    arr[rt].ms0 = Max(arr[rt].ms0,Max(Max(arr[rt].ls0,arr[rt].rs0),arr[rt<<1].rs0+arr[rt<<1|1].ls0));
}
void SWAP(int rt)
{
    Swap(arr[rt].ls1,arr[rt].ls0);
    Swap(arr[rt].rs1,arr[rt].rs0);
    Swap(arr[rt].ms1,arr[rt].ms0);
}
void down(int rt,int l,int r)
{
    if(arr[rt].down)
    {
        arr[rt].down^=1;
        arr[rt<<1].down^=1;
        arr[rt<<1|1].down^=1;
        SWAP(rt<<1),SWAP(rt<<1|1);
    }
}
void build(int rt,int l,int r)
{
    arr[rt].down = arr[rt].ls0 = arr[rt].ls1=arr[rt].ms0=arr[rt].ms1=arr[rt].ms0 =arr[rt].rs0=arr[rt].rs1= 0;
    if(l==r)
    {
        int v;
        scanf("%d",&v);
        if(v)
        {
            arr[rt].ls1 = arr[rt].rs1 = arr[rt].ms1 = 1;
        }
        else
        {
            arr[rt].ls0 = arr[rt].rs0 = arr[rt].ms0 = 1;
        }
        return ;
    }
    build(rt<<1,l,mid);
    build(rt<<1|1,mid+1,r);
    up(rt,l,r);
}
void update(int rt,int l,int r,int x,int y)
{
    if(x<=l&&r<=y)
    {
        arr[rt].down^=1;
        SWAP(rt);
        return ;
    }
    down(rt,l,r);
    if(x<=mid) update(rt<<1,l,mid,x,y);
    if(mid<y) update(rt<<1|1,mid+1,r,x,y);
    up(rt,l,r);
}
node query(int rt,int l ,int r,int x,int y)
{
    if(x<=l&&r<=y)
    {
        return arr[rt];
    }
    down(rt,l,r);
    if(x<=mid&&y>mid)
    {
        node tmp1 = query(rt<<1,l,mid,x,y);
        node tmp2 = query(rt<<1|1,mid+1,r,x,y);
        node ans;
        ans.ls1 = tmp1.ls1,ans.ls0 = tmp1.ls0;
        ans.rs0 = tmp2.rs0,ans.rs1 = tmp2.rs1;
        if(ans.ls1 == mid-l+1) ans.ls1+=tmp2.ls1;
        if(ans.ls0==mid-l+1) ans.ls0+=tmp2.ls0;
        if(ans.rs0==r-mid) ans.rs0+=tmp1.rs0;
        if(ans.rs1==r-mid) ans.rs1 += tmp1.rs1;
        ans.ms1 = Max(Max(Max(tmp1.ms1,tmp2.ms1),Max(ans.ls1,ans.rs1)),tmp1.rs1+tmp2.ls1);
        return ans;
    }
    else if(x<=mid)
    {
        return query(rt<<1,l,mid,x,y);
    }
    else if(x>mid)
    {
        return query(rt<<1|1,mid+1,r,x,y);
    }
}
int main()
{
    //ios::sync_with_stdio(false);
    //freopen("a.txt","r",stdin);
    //freopen("b.txt","w",stdout);
    int n,Q,opt,x,y;
    while(scanf("%d",&n)==1)
    {
        build(1,1,n);
        scanf("%d",&Q);
        while(Q--)
        {
            scanf("%d%d%d",&opt,&x,&y);
            if(opt==0)
            {
                printf("%d\n",query(1,1,n,x,y).ms1);
            }
            else
            {
                update(1,1,n,x,y);
            }
        }
    }
    //fclose(stdin);
    //fclose(stdout);
    //cout << "time: " << (long long)clock() * 1000 / CLOCKS_PER_SEC << " ms" << endl;
    return 0;
}


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